Annotation of /adduser.pl

changes from Siviwe Kwatsha <siviwe@plonkers.za.org>:
login and fullname: prompt until you have a "string" (something not enter)
passwd: fixed 2 typos on the variable name which break commandline,
only passwords NOT beginning with auth_ are encrypted
email: require a "word" before and after the '@', change error message to
reflect this can still get away with " name@address" but that's not strictly
wrong as the mua&/mta should strip it.